1. Technical Field
The present invention relates to a liquid discharging apparatus, a head unit, an integrated circuit device for capacitive load driving, a capacitive load driving circuit, and a manufacturing method of a liquid discharging apparatus.
2. Related Art
In a liquid discharging apparatus, such as an ink jet printer, which discharges ink and prints an image or a document, an apparatus which uses a piezoelectric element (for example, a piezo element) has been known. The piezoelectric elements are provided corresponding to each of a plurality of nozzles in a head unit, and each of the piezoelectric elements is driven in accordance with driving signals. Accordingly, a predetermined amount of ink (liquid) is discharged from the nozzle at a predetermined timing, and a dot is formed. Since the piezoelectric element is a capacitive load, such as a capacitor, in terms of electricity, it is necessary to supply a sufficient amount of current in order to operate the piezoelectric elements of each nozzle.
For this reason, in the above-described liquid discharging apparatus, the piezoelectric elements are driven as a driving signal which is amplified from a source signal for controlling the discharge input to a D/A conversion circuit, by an amplifying circuit is supplied to a head unit (ink jet head). An example of the amplifying circuit includes a type which performs current amplification with respect to a signal before the amplification by using a class-AB amplifier, and a type which performs voltage amplification by using a class-D amplifier, but the class-D amplifier is excellent in terms of energy efficiency.
In general, in order to prevent a voltage value of the driving signal from being shifted from a desired value due to unevenness in manufacturing, such as an offset of the D/A conversion circuit, or an offset or resistance of each amplifier included in the amplifying circuit, it is necessary to perform trimming. An example of a trimming method includes a method for adjusting a reference voltage (a high voltage side reference voltage and a low voltage side reference voltage) of the D/A conversion circuit in a predetermined voltage step so that the voltage value of the driving signal becomes the desired value. For example, in JP-A-2007-281776, a method for adjusting the reference voltage by using a trimming circuit for suppressing variation of the reference voltage of the D/A conversion circuit due to unevenness in manufacturing is suggested.
However, since the adjustment method suggested in JP-A-2007-281776 does not consider characteristics of the piezoelectric element, when the method is employed in adjusting the reference voltage of the D/A conversion circuit in the liquid discharging apparatus which uses the piezoelectric element as it is, there is a concern that an unnecessary increase in circuit scale or adjustment time of the circuit is caused.